Frank Ahrens: Why it's so hard for Toyota to find out what's wrong

I won't lie to you: I was not a good engineering student. That's one of the reasons I went into journalism. But I managed to acquire a bachelor of sciences in mechanical engineering, and the recent Toyota hearings on Capitol Hill brought back a lot of memories. Specifically, memories about how engineers figure out why mechanical things fail.

It was made painfully clear at the hearings that a number of lawmakers do not understand the process. An exchange between Del. Eleanor Holmes Norton (D-D.C.) and Toyota President Akio Toyoda illustrated the problem.

Toyoda said that when his company gets a complaint about a mechanical problem, engineers set to work trying to duplicate the problem in their labs to find out what went wrong.

Norton said: "Your answer -- we'll wait to see if this is duplicated -- is very troublesome." Norton asked Toyoda why his company waited until a problem recurred to try to diagnose it, which is exactly what he was not saying.

Members of Congress are generally lawyers and politicians, not engineers. But they are launching investigations and creating policies that have a direct impact on the designers and builders of incredibly complex vehicles -- there are 20,000 parts in a modern car -- so there are some basics they should understand. Chief among them: The only way to credibly figure out why something fails is to attempt to duplicate the failure under observable conditions. This is the engineering method.

"It's just so difficult for people to understand the complexity of the thing," said David E. Cole, chairman of the Center for Automotive Research in Michigan and an engineer. "They don't have the background. They don't have the time to do an investigation. They want to oversimplify a thing that can't be oversimplified."

Toyota is facing an incredibly difficult task. Here's what it knows: It has received hundreds of complaints about unintended acceleration in its vehicles in recent years. People have died in these crashes. Over the same period, hundreds more have died in Toyota crashes that had nothing to do with runaway acceleration. After that, it knows nothing.

Toyota must search its data and look for patterns or similarities among the incidents. Among dozens of variables, it must consider: